About 7 years ago, I bought my mom a rose bush that blooms small, yellow roses. It's bloomed these pretty, bright yellow flowers every year. Mom doesn't really do much to the plant itself, just waters it and cuts it back. She called me in a tizzy earlier because it has started to bloom but this year is blooming deep red flowers!!! Does anyone who knows about rose gardening have any explanation for this? I think it's a neat mystery but my poor mom's freaked out that they're suddenly living on contaminated ground!
I don't know about where you live, but Florida sells roses that are grafted onto wild rose plants. This is because the wild rose is sturdier growing. Have her look and see if the red rose branches are below the graft. If there is a graft, it is pretty easy to spot because is typically a lump at graft.